This section provides background information related to the present disclosure which is not necessarily prior art.
Display devices occupy an increasingly large fraction of surface area in many computing devices. Energy efficiency is becoming ever more important for a green and sustainable future. As global energy demand continues to grow to meet the needs and aspirations of people across the world, ways to improve energy efficiency and harvest energy are essential. However, little attention has been paid to the significant light energy wasted in displays used in everyday lives. For example, in the prevailing liquid crystal displays (LCD), only 3-8% of the backlight reaches a viewer's eyes, where most of light energy is absorbed by the colorant-based filters and polarizers.
Color and spectral imaging systems in display devices typically use filters and glass prisms to disperse light of different wavelengths. Transmissive optical filters are widely utilized in various display applications, including flat panel screens, like liquid crystal display (LCD) panels. Optical wavelength filters are devices that reflect or transmit light of a desired wavelength or within a certain wavelength range. For example, a transmissive filter selectively transmits light within a preselected wavelength transmission bandwidth, while absorbing or reflecting light of wavelengths outside the transmission bandwidth. Such optical filtering for wavelength provides a way to control the energy and spectral composition of light and is widely used in display applications.
To produce color images, existing display devices produce three primary colors, typically, red, green, and blue, collectively referred to as “RGB.” Conventional optical filters use pigment dispersions to filter and produce RGB colors for display pixels. Light of complementary colors are absorbed and completely wasted. Such optical filters are typically manufactured by four separate processes, which not only complicates manufacturing, but also wastes chemical materials in the process. Thus, such optical filters have relatively low energy efficiency, while adding significantly to the overall cost and size of the display device. Currently used polarizers in LCD displays achieve the polarization function by absorbing light of the orthogonal polarization and the absorbed light is also wasted.
With the miniaturization of integrated devices, there is a need for a new paradigm in color filter technology that can produce optical filters in the visible range with higher transmission efficiency and reduced manufacturing complexity to provide devices with high energy efficiency, low power consumption, and slim dimension. Furthermore, it would be desirable to have display devices capable of recycling or harvesting absorbed energy to generate useful electrical power, especially for devices such as electronic books that consume relatively small amounts of power, or mobile devices (such as cell phones) that are in standby mode 95% of the time.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.